Thank you so much to all who have responded to my questions it has been really helpful and comforting reading all your replies

Could you please explain to me in simple English how Bitcoin works?

Can you mine for Bitcoin and Ethereum on a single GPU rig at the same time?

How much does it cost to mine 1 Bitcoin (in the US)?

The 6 Biggest Risks to Bitcoin:

1. Bitcoin's blockchain loses its appeal
2. Brand-name businesses stop accepting bitcoin
3. A double-edged sword of regulation
4. A cyber attack hits Bitfinex (or another cryptocurrency exchange)
5. Margin mayhem derived from its CME listing
6. Investor emotions sack bitcoin

What should I do with my Bitcoins? I have 420 BTC.

So what exactly is this “blockchain”?